Cool, my advisor used to do research on New Britain, the neighbouring island.... well the reason why nobody has stepped forward to teach you Unserdeutsch, can be found in the Wikipedia article you mentioned: it is a dying language, now only spoken by 100 people, mostly elderly speakers... This is actually true for many of Papua-New Guinea's 800 or so languages, that the spread of Tok Pisin is creating more pressure on a lot of small languages there...

Since nobody seemed to upload any resources here, I took a little bit of my time finding for some, and stumbled upon this site.Rabaul Creole German (Unserdeutsch) Project by the University of Augsburg (in English)(auf Deutsch)It has some published works regarding the language, as well as audio recordings of the spoken language and photos of Vunapope, both from the older and more recent times.The project is still under active construction, so it may not be complete enough for you.

Jika saya ada salah, mohon diperbaiki. If I make a mistake or more, please correct me.Forever indebted to Robert A. Blust for his contributions to Austronesian linguistics(Native languages)~(East Javanese accent) (Non-fluent native language, currently learning)~ (Fluent second languages)~ (Understanding)~ (Learning/wanting to learn)~